high voltage - Why does arcing occur on helicopter power-line repair

I saw this video, where a guy did power line inspection from a helicopter, which is isolated from ground. When he held out a "magic wand," a small amount of arcing came off of the power line to the helicopter.

This got me confused, though, because I thought since he was isolated from ground, the power would not want to go anywhere.

The helicopter simply has no relationship to ground.

So, why does the Magic Wand arc to the helicopter?